The invention relates to a device and a method for preventing collisions between a vehicle and an obstacle when parking.
It is known to arrange one or more sensors in vehicles which detect the distance between the vehicle and an obstacle. If the distance from an obstacle drops below a limiting value, it is known to generate a signal, as a result of which a visual and/or audible indication is issued.
A disadvantage with this procedure is that it does not prevent the collision occurring. This is the case only if the driver reacts appropriately.
The object of the invention is therefore to ensure that a collision is reliably prevented without further intervention by the driver.
This object is achieved by means of the device according to the invention and by means of the method according to the invention, in accordance with the independent patent claims. Further advantageous refinements are contained in the subclaims.
In a device having at least one sensor for generating signals which represent the distance between the vehicle and an obstacle, these signals are processed in an evaluation unit. If at least one distance signal drops below a limiting value, an alarm signal is generated. By means of this alarm signal a control valve is actuated which generates a pressure difference between the working chamber and the partial vacuum chamber in a brake booster when the alarm signal is present. this pressure difference leads to a build-up of brake pressure in the wheel brake cylinders and thus causes the vehicle to decelerate to a standstill.
According to one advantageous development, when an alarm signal is not present the control valve serves as a conventional proportional valve which generates a pressure difference between the partial vacuum chamber and the working chamber of the brake booster which is proportional to the activation force of the brake pedal.
In accordance with the method according to the invention, the distance from an obstacle is sensed by means of at least one sensor in order to prevent collisions when parking the vehicle. If at least one distance signal drops below a limiting value, a brake pressure which causes the vehicle to come to a standstill is generated in wheel brakes.
According to one advantageous refinement, the brake pressure is maintained here until it is detected that the vehicle has come to a standstill. Further refinements present further switching-off criteria which must be present in addition to the vehicle being at a standstill so that the brake pressure is reduced. These are the switching of the gear lever, the activation of the clutch and the activation of the accelerator pedal by the driver. According to further subclaims, the brake pressure is progressively increased until the vehicle comes to a standstill. In order to reliably keep the vehicle at a standstill, according to a further refinement the brake pressure is increased further, but a specific amount is predefined for this increase.
According to an advantageous refinement which goes further, the collision monitoring is maintained for the period of the braking operation, and if the monitoring system detects the end of a risk of collision or a driver intervention to avert the collision (for example by means of a steering angle sensor), the automatic braking intervention can be aborted prematurely.